Because the organic electroluminescent diode (OLED) possesses advantages of self-luminous, fast response, wide viewing angle, high brightness and light weight, the potential market looks to further increase in the industry. The structure of the basic OLED mainly comprises an anode, a hole injection layer, a hole transporting layer, an emitting layer, an electron transporting layer, an electron injection layer and a cathode. The emitting layer of OLED has a concentration quenching. If a single emitting material is employed as an emitting layer, it will greatly reduce the light emitting efficiency thereof. At present, the OLED emitting layer is usually formed by the host and the dopant with a total evaporation.
The vacuum evaporation is a process of placing the material to be film into a vacuum environment for evaporation or sublimation to cause to precipitate on the surface of the substrate. The process generally comprises the process of thermal evaporation, and the flight process and deposition process of gasified atoms or molecules in the atmosphere. Before the deposition, the doping ratio of the dopant and the host is generally designed to be the ratio for maximally increasing the light emitting efficiency. However, in the flight process of gasified atoms or molecules in the vacuum evaporation, due to the different dissipation of the host material and the dopant material, the doping ratio of the final emitting material changes, and the light emitting efficiency is lowered.